(1) Field of the Invention
The present invention generally relates to an optical disk drive, and more particularly to an optical disk drive having a time code detection device which detects a time code of a recordable optical disk on the optical disk drive.
(2) Description of the Related Art
Compact disks, including a CD-R (compact disk-recordable), a CD-E (compact disk-erasable) and a CD-RW (compact disk-rewritable) are types of known optical disks. Generally, in the CD-R, data can be written only one time, and in the CD-E and the CD-RW, data can be written many times.
In a compact disk, a time code is written to a channel Q of a subcode, as part of recorded data of the disk, for each of a plurality of sectors (or blocks) of the disk. The time code indicates a current time with respect to one of the plurality of sectors (or blocks) of the disk.
FIG. 5 shows a format of a channel Q of a subcode of a compact disk.
As shown in FIG. 5, in the channel Q of the subcode, a subcode frame sync code "S0", a subcode frame sync code "S1", a control code, a track number, a time-in-track code, a time-in-disk code, and a CRC (cyclic redundancy check) code are provided. Each of the time-in-track code and the time-in-disk code includes a minute portion, a second portion, and a frame portion.
In a recordable optical disk of the above type, such as the CD-R or the CD-RW, pregrooves are provided as part of recorded data of the disk, and the pregrooves are used to indicate a time code which provides a reference position of the disk for starting writing of data to the disk. The pregrooves are formed so as to wobble on the disk in a sinusoidal pattern. The pregrooves provide a wobbling signal when the disk is accessed by an optical disk drive. Typically, the wobbling signal has its central frequency at 22.05 kHz. In order to indicate a time code for one of a plurality of sectors (or blocks) of the disk, the wobbling signal is frequency modulated in accordance with the time code, and its frequency modulation factor is set at .+-.1 kHz with the central frequency of 22.05 kHz.
The time code indicated by the wobbling signal of the pregrooves of the disk is called an ATIP (absolute time in pregroove) frame.
FIG. 6 shows a format of an ATIP frame of a recordable optical disk.
As shown in FIG. 6, in the ATIP frame, a sync code, a time-in-disk code, and a CRC (cyclic redundancy check) code are provided. The time-in-disk code includes a minute portion, a second portion, and a frame portion.
In an existing optical disk drive which is capable of rewriting data to a recordable optical disk, an ATIP frame is read from a current sector of the disk so that a time code of the ATIP frame for the current sector of the disk is detected. A position of the sector at which the rewriting of data to the disk is started is determined by the detected time code. In the recordable optical disk, data is recorded in a format which is the same as the format for recording of data in the compact disk shown in FIG. 5.
Japanese Laid-Open Patent Application No. 6-290462 discloses a time code detection device which detects a time code indicated by a wobbling signal of pregrooves of a compact disk.
However, after a time code is recorded in pregrooves of a recordable compact disk, such as the CD-R or the CD-RW, the wobbling signal of the pregrooves is influenced by the recorded data of the disk, and a signal-to-noise (S/N) ratio of the wobbling signal may be degraded. In a case in which the S/N ratio of the wobbling signal is significantly low, an error of demodulation of the ATIP frame may occur.
For example, when data is rewritten to a non-recorded area adjacent to recorded areas of the recordable compact disk, the demodulation error of the ATIP frame is likely to occur. In such a case, the time code detection device of the above-mentioned publication cannot provide a time code of the disk for the optical disk drive due to the demodulation error. The optical disk drive cannot reliably perform a writing operation for the disk.
It is difficult for the time code detection device of the above-mentioned publication to reliably provide a time code of a recordable compact disk for the optical disk drive when an error of the time code has occurred.